In recent years, with rapid spread of information-related equipment and communication equipment such as personal computers, video cameras, and mobile phones, the development of batteries used as a power source therefor has been emphasized. Further, also in the automobile industry and other industries, the development of batteries having high output and high capacity for electric vehicles or hybrid vehicles has been advanced. Among various batteries, a lithium battery has been presently noticed from the viewpoint of a high energy density.
A liquid electrolyte containing a flammable organic solvent is used for a presently commercialized lithium battery, so that the installation of a safety device for restraining temperature rise during a short circuit and an apparatus for preventing a short circuit are necessary therefor. To the contrary, a lithium battery all-solidified by replacing the liquid electrolyte with a solid electrolyte layer is conceived to intend the simplification of the safety device and be excellent in production cost and productivity for the reason that the flammable organic solvent is not used in the battery.
A sulfide solid electrolyte material has been known as a solid electrolyte material used for an all solid lithium battery. For example, Patent Literature 1 discloses a LiSiPS-based sulfide solid electrolyte material (argyrodite type). Further, for example, Patent Literature 2 discloses a sulfide solid electrolyte material having a composition of Li(4-x)Ge(1-x)PxS4.